It is well known to treat patients with medicaments contained in an aerosol, for example in bronchodilator therapy, by means of an inhalation device. Such devices typically comprise a tubular housing, in which the aerosol container is located with a support, and an outlet tube generally in the form of a mouthpiece leading from the tubular housing. The aerosol containers used in such inhalation devices are designed to deliver a predetermined dose of medicament upon each actuation. When used for dispensing medicaments, the housing is held by the patient in a more or less upright position and the mouthpiece is placed in the mouth of the patient. The aerosol container is pressed towards the support to dispense a dose of medicament from the container which is then inhaled by the patient.
It may be understood that effective delivery of medicament to the patient using an inhalation device as described above is dependent upon the patient's ability to coordinate the actuation of the device with the taking of a sufficiently strong inward breath. The required co-ordination can present difficulties to many patients, particularly young children and the elderly, with the risk that these patients do not receive the appropriate dose of medicament. It is thus desirable to provide a means for the patient and medical professional to monitor the usage of the inhalation device. Such means might be designed for everyday usage, or for use in a system for training patients in the correct operation of the inhaler.
One approach to developing such a training system would be to provide a means for comparing the patient's ability to operate the inhaler, for example as assessed by pressure release profiles, against standard criteria for a given inhaler and to advise the patient accordingly in the use of the inhaler. Such pressure release profiles would be determined by measuring the duration and intensity of the patient's inhalation pressure within the body of the inhaler, together with that on firing the container. However, a technical problem in adopting this approach is encountered in trying to differentiate between the inhalation and firing pressures which coincide as they differ greatly in intensity, leading to inaccuracies in their measurement.
The Applicants have now found that inhalation and actuation pressures in an inhalation device may be individually measured by use of two pressure recorders or transducers connected to separate outlet ports within the housing of the device. The pressure recorders can be connected to a microprocessor which can record the output from the pressure recorders and compare the patient's pressure release profile with standard profiles for the inhaler. Suitable instructions are then issued to the patient on a visual display unit advising them in the operation of the inhalation device. The housing, as described below, may be used in a system by medical professionals to train patients in the correct usage of an inhalation device.
The advantage of the present invention over existing methods which employ a pressure sensor to measure actuation is that the use of two physically separated outlet ports in the housing body enables direct measurement of the inhalation and firing pressures.
This in turn allows for more accurate and reproducible measurement of both the pressures and the timings involved in determining pressure release profiles as opposed to previous methods which involve indirect determination of such profiles.
The use of pressure recorders to measure actuation of inhalation devices is known in the art. For example, in WO 96/16686 a pressure transducer is employed in an inhalation device to record the number of doses used or remaining within the device.
International Application Number PCT/EP99/06249 discloses an indirect method of determining pressure release profiles on dispensing medicament to an inhaling patient by the use of two pressure transducers.
WO 93/12823 describes an inhalation device which provides feedback on its use to both the patient and to the medical professional. The device may be used to instruct patients in the correct operation of the inhaler and can also be employed to monitor patient usage over a fixed period.
The use of air flow sensors and differential pressure transducers within an inhalation device is also disclosed in U.S. Pat. No. 5,735,263. The sensors are used to determine a patient's inspiratory flow profile which is then compared to a standard profile by microprocessor means to assess the optimum time for drug release.